Sensor devices often need to store information or data internally for use by the sensor at certain times or in the occurrence of certain events. For example, magnetic field sensors often generate and store calibration information for use at start-up or some other time.
This stored information can be lost, however, if the sensor device experiences a reset event or loss of power. Returning to the magnetic field sensor example, these sensors are often used in automotive applications, such as fuel injection and other engine systems, where they can be exposed to significant electromagnetic interference, voltage spikes related to engine starts and stops or other sources, or other power interruptions. These interruptions can cause the supply line voltage to drop below the minimum necessary for the sensor, even for a very brief period of time, causing the sensor to reset and current calibration information to be lost. This is undesirable because a cold start of the sensor requires a calibration procedure, which takes additional time and cannot take into account calibration information obtained during actual operation conditions, which can capture, e.g., temperature and other real-time characteristics which vary from start-up or generally over time.
A related problem is corruption of calibration information. If the sensor is writing to memory when a loss of power or reset occurs, the information may nevertheless be written to memory but that information may be incomplete or corrupted. Even if the sensor is able to maintain the information after the power interruption, such as by using an external capacitor as a source of power, the sensor cannot know that the information is unreliable or uncorrupted. Using that information can lead to reduced performance or errors in the sensor, which are undesirable for obvious reasons.
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.